Access networks connect business and residential subscribers to the central offices of service providers, which in turn are connected to metropolitan area networks (MANs) or wide area networks (WANs). Often, these access networks are hybrid fiber coax (HFC) systems with an optical fiber based feeder network between the central office and a remote node, and an electrical distribution network between the remote node and subscribers. In so-called “Fiber-to-the-x” (FTTx) access networks, the copper-based distribution part of the access network is replaced with optical fiber, e.g., fiber-to-the-curb (FTTC) or fiber-to-the-home (FTTH). In doing so, the capacity of the access network is increased.
Passive optical networks (PONs) are optical networks that can be used in such applications. A PON is a point-to-multipoint, fiber to the premises network architecture in which unpowered optical splitters are used to enable a single optical fiber to serve multiple premises. A PON consists of an optical line terminal (OLT) at the service provider's central office and a number of optical network units (ONUs) near end users. A PON configuration can reduce the amount of fiber and central office equipment required compared with point to point architectures. Examples of types of PONs that are defined by international standard bodies include Ethernet Passive Optical Networks (EPONs) and Gigabit Passive Optical Networks (GPONs).
Reducing power consumption in one or more components of a PON is desirable. For example, utilizing an ONU that consumes less power provides a business advantage. Moreover, there may be regulations placing limitations on the amount of power consumed in PONs.
In one proposed method for reducing power consumption in an ONU, the OLT transmits to the ONU a special Operation, Administration, and Management (OAM) frame that instructs the ONU to enter a “power saving mode” in which the ONU reduces power to its subsystems. The ONU remains in the power saving mode until a timer expires. During the power saving mode, the ONU does not transmit data to the OLT, even if it is granted a window to transmit the data and has data to transmit.
Like reference numerals are used in different figures to denote similar elements.